The proposed research will provide information concerning the role that tyrosine, dopa, and dopamine play in neurobiological and reproductive processes of S. mansoni and F. hepatica. The uptake, distribution and metabolism of these three compounds by schistosomes will be studied both in (in vivo) and out (in vitro) of the host. In vitro studies will emphasize the extent to which these 3 compounds are incorporated into the schistosome egg. An enzyme, dopa oxidase, associated with egg production in female schistosomes will be characterized and then the activity of the enzyme will be measured in the presence of disulfiram, a drug which suppresses egg production. Further studies on the egg suppressant activity of disulfiram will determine the effects of this drug on tyrosine metabolism and oxygen consumption by S. mansoni, and egg production and dopa oxidase activity in F. hepatica. In addition, we will attempt to find structural analogs of disulfiram that are more potent in suppressing egg production by S. mansoni. Physiological processes, within adult S. mansoni and F. hepatica, which depend upon the presence of dopamine and norepinephrine will be studied by examining the effects of drugs which deplete these amines from these two trematodes. Drugs which deplete these amine in adult parasites will be given to the host before infection to determine if they will alter the development of the parasite within host.